Browsing by Author "Sivagnanam, Mohan"

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    Analysis of Flow and Heat Transfer in OTSGs and Injection Wells
    (2023-04-21) Sivagnanam, Mohan; Gates, Ian Donald; Mehrotra, Anil Kumar; Hejazi, Hossein; Ponnurangam, Sathish; Mwesigye, Aggrey; Sanders, Sean R.
    Steam for enhanced oil recovery, generated by using once-through steam generators (OTSGs), is injected into extra heavy oil (bitumen) bearing formations to raise the temperature of the oil within. At elevated temperatures, the oil mobility is raised enabling it to be produced to surface. To improve the performance of steam-based processes, the research documented here focuses on two components of the process. The first component is steam generation in OTSGs and the second is injection of steam into the reservoir. More specifically, in the first component, the impact of foulant is examined and how a deliberate flow perturbation can be used to delay the onset of foulant. In the second component, steam flows through slotted liners and flow control devices are investigated. The results show that the thicker the foulant, the higher the outer tube wall temperature and the lower is the water temperature – the foulant acts as an insulator on the inner wall of the tube. Flow perturbations are demonstrated to yield benefits for lowering the outer tube wall temperature. An examination of thermocouples used to measure the temperature of the tube surface in OTSGs is also presented. Simulation results for a thermocouple welded on an OTSG tube showed a discrepancy between the actual temperature and the thermocouple measurement. The use of a radiation shield is shown to provide a better estimate of the bare tube temperature. The analysis of a slotted liner shows that the slot area plays a crucial role in flow distribution within the well and reservoir. Supersonic flow in flow control devices is strongly dependent on steam quality and some of the systems examined exhibited a condensation shock and shock diamonds with exit velocity greater than the inlet. A longer diffuser is shown to minimize the impact of shock waves on the exit velocity.
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    PDC Drill Bit Redesign and Simulation for Optimized Performance
    (2014-08-29) Sivagnanam, Mohan; Martinuzzi, Robert; Hareland, Geir
    Polycrystalline diamond compact (PDC) drill bit design influences the bit hydraulics and hence the drilling performance. To improve the hydraulics, the fluid flow pattern across the drill bit should be optimized for low pressure drop, low recirculation flow and high velocity. Design of Experiments (DOE) was used to study the effect of various design parameters. Computational Fluid Dynamics (CFD) was used to simulate the fluid flow in the complex geometry of the drill bit. Response Surface Methodology was applied to optimize the design parameters for improved bit hydraulics. Preliminary simulations were conducted by increasing the complexity to meet the real time operation. Simulations based on fractional factorial experiment were used to identify the significant factors from the 15 design parameters. The optimum limits of the most significant five factors were identified from simulations based on central composite design (CCD). The optimization procedure was assessed by comparing the optimum design with the original design for Newtonian and Non-Newtonian conditions.